IRJET- Cost Comparison of different Grid Patterns of Floor Slab of Same Span

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 05 | May 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 416
COST COMPARISON OF DIFFERENT GRID PATTERNS OF FLOOR SLAB OF
SAME SPAN
Ritesh Meshram1, Prof. Kuldeep Dabhekar2, Er. Aashish Soni3
1M.Tesh Student (Structural Engineering, GHRCE Nagpur, India)
2Assistant Professor (Department of Civil Engineering, GHRCE Nagpur, India)
---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - A grid is a planar structural system composed of
continuous members that either intersect or cross each other
.Grids are used to cover large column free areas. Grids in
addition provide aesthetically pleasing appearance to the
roofs. These slabs are most preferred for publicassemblyhalls,
theatres, marriage halls, etc as it covers large column free
area. This type of structure is monolithic and has more
stiffness. It is beneficial over normal beams as it has a better
load dispersing mechanism and also this system reduces the
normal span to depth ratio which helps in reducing the height
of the building. It has been constructed in number of areas in
India n abroad. In the present study we have considered two
types of grid patterns, first is two way grid pattern and second
is diagonal grid pattern. The structure is analysed and
designed with the help of staad pro software. Design has been
checked with respect to IS 456-2000 code.
Key Words: Grids, STAAD PRO, IS 456-2000 Code, Span
to depth ratio, monolithic, stiffness.
1.INTRODUCTION
As we know in India, the structural cost of work is increases
time to time due to increase in material & labor cost, which
ultimately lead to increase the total cost of building. The
structural cost of work is approximately 50% of the total
cost of the building. So it is very essential to reduce the
structural cost of building. It can be possible by providing
safe & economical grid pattern of floors of building. In India
it is popular structural configuration often deployed in the
construction of hotel porticos, airport terminal buildings,
large banquet hall, convention centres and car parks. The
rectangular or square voids that are formed in the ceiling is
advantageously utilized for concealed architectural lighting.
The sizes of beams running in perpendicular directions are
generally kept the same. Instead of rectangular beam grid, a
diagonal.
1.1 TWO WAY GRIDS:
In two way grid pattern of floor slab the beams are ofsimilar
sizes and they intersect each other in both directions and
also they are at equally spaced intervals. These structures
are rigid planar oten monolithic structures that disperse
loads in multi directional pattern, with the loads generally
following the shortest stiffest routes to the supports.
Fig No.1
1.2 DIAGONAL GRIDS
The construction of egg crate is also not as efficient as
diagonal grid system. These gridsintersectbeamsdiagonally
but they are perpendicular to each other. It is required to
support the grid at four points only. The diagonal grid has
greater torsional rigidity. The sizes of grid beams are
normally similar and are also equally spaced.
Fig No.2

2. METHODOLOGY
In this study we have considered three different grid
patterns of beams on a floor slab of same area of 12 x 12m
span. The grid that we have used are Two way grids and
Diagonal. Second step is we have prepared the Models ofthe
all the grid patterns that we have consisdered using STAAD-
PRO V8i software. Model is also checked as per checks
available in the software. Third step is analysisanddesign of
the structure using STAAD- PRO V8i software. The design is
also manually checked and verified as per IS 456- 2000 code
for RCC design. The steps for analysis are given as follows,
a) To apply self weight of the structureinthesoftware.
b) To find shear force of the members.
c) To find Bending moments of the members.
d) To find the Displacements of the members.
Fourth step is to estimate the quantity of steel and concrete
required for all three structures manually. Final step is to
find the Structural cost of the building and respectively find
the per square feet cost of the building in terms of structural
cost.
A. Grid Patterns:-
Grid A (Two way grid)
Columns:
R1- 300x600 mm
R3- 300x300 mm
Beams:
R3- 300x750 mm
R4- 230x400 mm
Fig No.5 PATTERN 1
Grid B ( Diagonal grid)
Columns:
R1- 400x400 mm
Beams:
R2- 230x450 mm
R3- 300x600 mm
R4- 300x600 mm
R5- 300x600 mm
Fig No.6 PATTERN 2
3. LOAD CALCULATIONS
TWO WAY GRID:
DEAD LOADS (IS 875 PART-1)
Dead loads are loads that are permanent on the structure
such as construction materials and the materials which are
kept permanent on the structure. Also self weight of the
structure is considered as dead load.
Self weight :- Selft weight load- Direction Y- Factor = -1
Wall loads:-
Thickness of wall = 230 mm
Floor to floor height = 4m
Height of wall = 3.6m
Load calculation = 0.23 x 20 x 3.6
= 16.56 kN/m

Slab weight calculations :-
Thickness of slab = 125mm
Density of concrete = 25kN/cu.m
Self weight of slab = 0.125 x 25 = 3.125 kN/sq.m
Floor finish = 1.5 kN/sq.m
Total slab weight at floor level = 3.125+1.5= 4.625 kN/sq.m
LIVE LOADS (IS 875 PART 2)
Live loads are produced due to use and occupancy of
building. These are normally due to human occupants,
storage, furnishings, etc.
Live Load intensity specified = 4 kN/sq.m
LOAD COMBINATIONS:
Type L/C Name
Primary 1 DL
Primary 2 LL
Combinations 3 1.5(DL+LL)
DIAGONAL GRIDS :
Wall loads:-
Thickness of wall = 230 mm
Floor to floor height = 4m
Height of wall = 3.55m
Load calculation = 0.23 x 20 x 3.55
= 16.33 kN/m
Slab weight calculations :-
Thickness of slab = 125mm
Density of concrete = 25kN/cu.m
Self weight of slab = 0.125 x 25 = 3.125 kN/sq.m
Floor finish = 1.5 kN/sq.m
Total slab weight at floor level = 3.125+1.5= 4.625 kN/sq.m
LIVE LOADS (IS 875 PART 2)
Live loads are produced due to use and occupancy of
building. These are normally due to human occupants,
storage, furnishings, etc.
Live Load intensity specified = 4 kN/sq.m
4. ANALYSIS AS PER STAAD PRO
Table -1: Sample Table format
Preparation of Manuscript
Grids
Size of
members(in
mm)
Deflecti
on (in
mm)
Max B.M
(in Kn.m)
Max S.F
(in Kn)
G1 Beams:
R4- 230x400
R2- 300x750
Columns:
R3- 300x300
R1- 300x600
Slab thickness=
125mm
0.735
15.033
45.453
280.806
9.234
275.815
68.876
189.668
3.439
101.185
G2
Columns:
R1- 400x400
mm
Beams:
R2- 230x450
mm
R3- 300x600
mm
R4- 300x600
mm
R5- 300x600
mm
2.40
5.43
15.49
20.87
177.43
51.56
193.30
226.81
167.73
94.50
65.16
142.10
134.87
116.82

5. DESIGN
DESIGN PARAMETERS:
As per IS 456-2000 code these design parameters has been
set in STAAD PRO V8i software.
a) Brace: Beam/Column braced in both directions
b) Clear cover: for column = 40mm
for beam = 30 mm
c) Ely: Min length factor about local Y direction = 1
d) Elz: Min length factor about local Y direction = 1
e) Fc: compressive strength of concrete=25N/sq.mm
f) Fy main: 500 N/sq.mm
g) Fy sec: 500 N/sq.mm
h) Max main: 32mm
i) Min main: 12mm
j) Max sec: 10mm
k) Min sec: 8mm
l) Ratio: Max percentage of longitudinal
reinforcement allowed = 4
m) R face: Longitudinal reinforcementincolumnalong
four faces
n) Torsion: Design for torsion
o) Track: Beam and column minimumdetails
are printed
p) Commands: Design Beam, Design column.
Two way grid pattern (G1)
Column design:
Beam design:
2) Diagonal grid pattern (G2):
Schedule of beams:
Schedule of columns:
Schedule of slabs:
6. ESTIMATION
Grid A: CONCRETE QUANTITY :
Size of members No. L (m) B
(m)
D (m) Qty
(cu.m)
Beams
R2(300x750mm) 6 11.40 0.30 0.625 12.825
R4(230x400mm) 16 10.5 0.23 0.275 10.626
Columns

R3(300x300mm) 4 3.6 0.3 0.3 1.296
R1(300x600mm) 12 3.6 0.3 0.6 7.776
Slab 1 10.5 10.5 0.125 13.78
Deductions 9 0.3 0.625 1.685
Total qty 44.618
REINFORCEMENT QUANTITY:
FOR COLUMN:
Description Dia No. L(m) wt/m Qty (kg)
C1 12 8 4 0.89 28.48
C2 12
16
6
6
4
4
0.89
1.58
21.36
37.92
Lateral ties 8 28 1.040 0.395 11.50
Total 99.26
FOR BEAMS:
For R4: 230x400 mm
Description Dia No. L(m) wt/m Qty (kg) Total
Qty(kg)
Bott. Bars 12 2 13.20 0.89 23.49 93.98
Cut at
middle
2/3*L
12 1 8 0.89 7.12 28.48
Top bars 12 2 13.20 0.89 23.49 93.98
Extra top 12 1 7.2 0.89 6.408 25.632
Stirrups 8 80 1.112 0.395 35.14
Total 277.212
For R2: 300x750 mm
Descripti
on
Di
a
No
.
L(m) wt
/m
Qty (kg) Total
Qty(k
g)
Bott
Bars
25 3 14.5 3.8
5
55.94x3=16
7.82
1006.
92
Cut at
middle
2/3*L
25 3 8 3.8
5
30.8x3=92.4 554.4
Top bars 25 2 14.5 3.8
5
55.94x3=16
7.82
1006.
92
Extra
top
25 3 3.6 3.8
5
13.86x3=
41.58
249.4
8
Stirrups 8 12
0
1.96
0
0.3
95
92.91
Total 2910
For slab:
No. of bars required = 22
Straight bars = 11
Bent up bars = 11
Cutting length of bent up bars = L + 0.42H + Ld – bends
Here, H = D – (2 x clear cover) – diameter of bar
= 125 – (2 x 20) – 8 = 77
Cutting length of bent up bars = 3.34 m
Cutting length of straight bars = L + Ld
= 3000 + (45 x 8)
= 3.36 m
Distribution reinforcement:
No. of bars required = 22
Extra reinforcement = 8
Cutting length = L – (2 x 0.3L) + (2 x spacing)

= 3000 – (2 x 900) + 300
= 1.5 m
Description Dia No. L(m) wt/m Qty
(kg)
Total
Qty(kg)
Bent up bar 8 11 3.34 0.3950 14.51
Straight bars 8 11 3.36 0.3950 14.6
Distribution
reinforcement
8 22 3.36 0.3950 29.19
Extra
reinforcement
8 8 1.5 0.3950 4.74
Summation 63.04
x 2
126.08
Total 2017.28
TOTAL QUANTITY OF STEEL = 5303 kg
Grid G2 : CONCRETE QUANTITY
Beam(mm) No. L B D Qty.(cu.m)
R2-
230x450
4 12.40 0.23 0.325 3.707
R3-
300x600
4 5.65 0.3 0.475 3.22
R4-
300x600
4 11.31 0.3 0.475 6.44
R5-
300x600
2 16.97 0.3 0.475 4.83
Slab 1 12.23 12.23 0.125 18.69
Column-
400x400
12 3.55 0.4 0.4 6.816
Total
A
43.70
Deductions
Junction of
beams
R3 & R5 4 0.3 0.3 0.475 0.171
R4 & R4 4 0.3 0.3 0.475 0.171
R4 & R5 4 0.3 0.3 0.475 0.171
R5 & R5 1 0.3 0.3 0.475 0.04275
Total
B
0.55
NET
QTY. = 43.15 cum
The steel quantities can be calculated as calculated for Grid
pattern G1. So here is the quantity estimate of steel of grid
pattern G2,
Di
a
Colm.
(m)
Beam
(m)
Slab
(m)
Total
(m)
Wt
(kg/m)
Total
(kg)
8 20.16 1900 3100 0.395 2142
16 345.60 312 657 1.58 1039
25 528.56 528.56 3.58 1894
32 210.24 210.24 6.320 1328
Total 6403
7. CONCLUSION
COST COMPARISON:
GRID
NO.
C.C
QT
Y.
RATE
7200/
-
Steel
QTY.
(M.T)
RATE
Rs.60,000
/M.T
Total
Amou
nt
COST
PER
SQUAR
E FEET
1 44.
618
3,21,2
49/-
5.303 3,18,180/
-
6,39,4
29/-
4,440/-
2 43.
15
3,10,6
80/-
6.403 3,84,180/
-
6,94,8
60/-
4,825/-
3 47.
90
3,44,8
80/-
6.727 4,03,620/
-
74850
0/-
5,197/-

 The quantity of concrete required for grid 1 is
44.618 and steel quantity is 5.303 M.T and cost per
square feet is 4400/-.
 The quantity of concrete required for grid2is43.15
and steel quantity is 6.403 M.T and cost per square
feet is 4825/-.
Thus we conclude that TWO WAY GRID PATTERN is
economical cost wise as well as steel and concrete wise as
compared to DIAGONAL GRID. But for architectural view
purpose some may use Diagonal grid pattern as its
aappearance is good as compared to two way grid pattern.
Torsional rigidity of Diagonal grid pattern is good as
compared to two way grids. There sre several grid patterns
that can be used and each grid pattern has different
significance on the structure. But they are way good
compared to Buildings with no. of columns.Thus, Wecan cut
the structural cost of the building by providing grid patterns
of floor slabs.
CONCRETE QTY COMPARISON
STEEL QTY COMPARISON
COST COMPARISON
REFERENCES
 Amick, H., Hardash, S., Gillett, P., and Reaveley, R.
(1991). “Design of Stiff,Low-VibrationFloorStructures.”
Proceedings of International Society for Optical
Engineering (SPIE), 1619,180-191
 Das, B. (2010), “Static and Dynamic Analysis of Grid
Beams,” thesis, presented to National Institute of
Technology Rourkela, in partial fulfillment of the
requirements for the award of bachelors of technology
degree in civil engineering.
 IS 456 (2000). “Indian Standard Plain Reinforced
Concrete Code of Practice”, Fourth Revision, Bureau of
Indian Standards (BIS), New Delhi.
 IS 875 (1987). “Indian Standard CodeofPracticefor
Design Loads (Other Than Earthquakes) For Building
and Structures Part 2: ImposedLoads”,SecondRevision,
Bureau of Indian Standards (BIS), New Delhi.
 Ozturk, T., and Ozturk, Z. (2008). “The effects of the
type of slab on structural system in the multi storey
reinforced concrete buildings.” Proceedings of the 14th
World Conference on Earthquake Engineering, Beijing,
China, October 12-17.
 Patel, H., and Vepari,I.(2011).“Studyon economical
aspects of long span slabs.” National Conference on
Recent Trends in Engineering and Technology, B.V.M.
Engineering College, V.V. Nagar, Gujarat, India, May 13-
14.
 Sathawane, A., and Deotale, R. (2011).“Analysisand
Design of Flat Slab and Grid Slab and their cost
comparison.” International Journal of Engineering
Research and Applications, 1, 837-848.
 STAAD-Pro (2008). Structural analysis software,
“Static and Dynamic Finite Element Analysis of
Structures.” Bentley, USA.

IRJET- Cost Comparison of different Grid Patterns of Floor Slab of Same Span

Recommended

Recommended

More Related Content

What's hot

What's hot (19)

Similar to IRJET- Cost Comparison of different Grid Patterns of Floor Slab of Same Span

Similar to IRJET- Cost Comparison of different Grid Patterns of Floor Slab of Same Span (20)

More from IRJET Journal

More from IRJET Journal (20)

Recently uploaded

Recently uploaded (20)

IRJET- Cost Comparison of different Grid Patterns of Floor Slab of Same Span